Method of and means for rolling rods

ABSTRACT

A metal rod to be used as a concrete armature is passed between a pair of counterrotating shaping rollers with complementary peripheral channels of substantially semicircular cross-section transversed by rib-forming grooves. The grooves merge with the channel surface along rounded edges, with the radius of curvature at the leading edge (as seen in the direction of roller rotation) smaller than that at the trailing edge; conversely, the angle included between the roller periphery and the front flank of each groove is larger than the desired leading angle of the rib whereas the angle included between the roller periphery and the rear flank of each groove is smaller than the desired trailing angle of the rib.

United States Patent Bock, deceased et al.

[ 51 Apr. 4, 1972 [54] METHOD OF AND MEANS FOR ROLLING RODS [72] Inventors: Ernst Bock, deceased, late of Peine, Germany by lngeborg Bock, administratrix; Martin Majewski; Wilhelm Bartels, both of Peine, Germany [73] Assignee: llseder Hutte, Peine/Hann., Germanyby said Majewski and said Bartels [22] Filed: July 23, 1970 [211 App]. No.: 57,620

[30] Foreign Application Priority Data .Iu1y26, 1969 Germany P 19 38 120.5

US. Cl ..72/198, 72/366 Field of Search ..72/194, 198, l99, 365, 366

[56] References Cited UNITED STATES PATENTS 2,377,980 6/1945 Surerus ..72/198 2,552,364 5/1951 Bradbury.. ...72/l98 3,494,164 2/1970 Rehm et al ..72/ 194 Primary Examiner-Lowell A. Larson Attorney-Karl F. Ross ABSTRACT A metal rod to be used as a concrete armature is passed between a pair of counterrotating shaping rollers with comple- -mentary peripheral channels of substantially semicircular cross-section transversed by rib-forming grooves. The grooves merge with the channel surface along rounded edges, with the radius of curvature at the leading edge (as seen in the direction of roller rotation) smaller than that at the trailing edge; conversely, the angle included between the roller periphery and the front flank of each groove is larger than the desired leading angle of the rib whereas the angle included between the roller periphery and the rear flank of each groove is smaller than the desired trailing angle of the rib.

6 Claims, 6 Drawing Figures PATENTEDAPR 41972 3, 653 ,246

SHEET 2 BF 3 Erns'r Bock Marfin Mqjewski Wilhelm Barfels Inventors.

B y K Attorney PATENTEUAPR 41972 3, 653 246 SHEET 3 OF 3 Ernst Bock Marfin M 'ewski Wilhelm arfels lnveniam 9 Attomey The present invention relates to a method of and means for shaping metal rods, usually of steel, to produce ribbed elements known as deformed bars which can be used as armatures in the reinforcement or prestressing of concrete structures.

It is known to use a pair of counterrotating, suitably profiled rollers to produce such ribs on opposite sides of a metal rod advancing continuously through the ribs of the rollers. The roller profile forms a peripheral channel of substantially semicircular cross-section interrupted by several generally transverse grooves whose shape is, in first approximation, complementary to that of the ribs to be formed. Each rib may span the entire or nearly the entire semicircular rod surface deformed by one of the rollers and may be of constant height or taper toward that surface at its ends. The ribs, in addition to resisting dislodgment of the rod from a concrete structure in which it is imbedded, also serve as anchor points for terminal members or couplings used in prestressing or in interconnecting several rods to form an armature of increased length.

If the ribs lie in planes perpendicular to the rod axis, the terminal members or couplings can be designed as split sleeves whose halves, provided with grooves complementary to the ribs, are clamped together around the rod or rods. If the ribs extend along helicoidal lines, these elements can be internally threaded and adapted to be screwed onto the rod in the manner of a nut.

In all these instances, the ribs ought to be able to resist considerable axial shear stresses in both directions so that a continuous transition between the rod surface and the ribs is essential to prevent excessive stress concentration. It is there fore desirable that the flanks of each rib should be faired into the rod surface with a radius of curvature at the root of each flank which should be substantially the same for both sides of the ribs (as measured in an axial plane of the rod bisecting the rib). The angles of inclination of the flanks with reference to the baseline of the rib (in the aforementioned axial plane) may or may not be alike, depending on whether the expected axial stresses are equal or different in the two directions. In any event, however, these flanks should rise substantially tangentially from the rounds at the root of the ribs.

The obvious way of realizing such rib profiles appears to be an exactly complementary shaping of the corresponding roller grooves at least in the vicinity of the channels roller periphery. Experimentation has shown, however, that a progressive deformation of the rod, which is extruded from the nip of the rollers at a speed higher than its speed of advance toward the rollers, distorts the shape of the rib with a resulting decrease in the angle of inclination of the leading flank and a corresponding increase in the angle of inclination of the trailing flank as seen in the direction of rod motion which, of course, coincides with the circumferential motion of the rollers at the point of contact. This tilting of the ribs also involves an increase in the radius of curvature at the root of the rib on its front side and a corresponding decrease of that radius on its rear side.

The object of this invention, therefore, is to improve the existing technique of rolling ribbed rods to avoid the aforestated drawbacks and to provide guidelines for the convenient realization of a desired rib profile satisfying the usual mechanical requirements.

This object is attained, in accordance with the present invention, by fairing the flanks of each roller groove into its channel surface along rounded leading and trailing edges (as seen in the direction of roller rotation) whose radii of curvature differ sufficiently to compensate for the aforedescribed rib deformation due to the increased extrusion speed of the rod. Thus, the round of the leading edge (as viewed in the direction of rotation and within a plane of symmetry transverse to the roller axis which coincides with an axial plane of the rod) should have a substantially smaller radius of curvature than the round of the trailing edge.

In the rolling of concrete armatures conforming to present standards, the extrusion speed of the rod exiting from the nip of the rollers exceeds its entry speed by about 4 percent to 7 percent. Under these circumstances, the radius of curvature at the leading edge of each groove should range between substantially three-quarters and one-half of the radius of curvature of the trailing edge.

By the same token, the angle of inclination of the side of each groove with reference to the roller periphery should differ from the design angles of inclination of the corresponding rib sides, and therefore from each other if the rib profile is to be symmetrical. It has been found, in accordance with the present invention, that the front angle of the groove should exceed the rear angle by about 5 percent to 15 percent, in the range of relative extrusion speeds specified above, in order to produce a rib whose flanks rise from the rod surface at substantially identical angles.

The invention will be described in greater detail with reference to the accompanying drawing in which:

FIG. 1 is a sectional elevational view of a pair of counterrotating rollers (shown only in part) in the process of deforming a rod;

FIG. 2 is a sideview of a deformed rod with helicoidal ribs shaped by the rollers of FIG. 1;

FIG. 3 is an enlarged fragmentary sectional view of the rod and one of the rollers;

FIG. 4 is a diagrammatic view drawn to a still larger scale and showing the shape of a rib produced by the rollers of FIGS. 1 and 2 with conventionally designed grooves; and

FIGS. 5 and 6 are views similar to FIGS. 3 and 4, respectively, illustrating the formation of ribs in accordance with the present improvement. I

In FIG. 1 there is shown a steel rod 2 moving, in the direction of arrow A, into the bite of two counterrotating rollers l and l' turning clockwise (arrow B) and counterclockwise (arrow B), respectively. The two rollers have complementary peripheral channels 8 and 8' interrupted by generally transverse grooves 7 and 7, respectively.

FIG. 2 shows part of a finished rod 2 with ribs 3 and 3' formed thereon by the grooves 7 and 7' of rollers I and 1 (FIG. 1). The ribs are shown to form a nearly continuous helicoidal thread engageable by an internally threaded sleeve or nut.

FIGS. 3 and 4 illustrate in greater detail the shaping of the ribs 3 by the grooves 7. These grooves are shown to have symmetrical profiles within an axial plane of rod 2 bisecting the roller 1, with the front flank 4 of each groove in that plane merging tangentially into a rounded edge 5 of radius r and with the rear flank 6 similarly merging into a rounded edge 9 of radius r The two radii r and r, are identical and the angles a and B included between the flanks 4, 6 and the rod surface at the point of contact are also alike; a roller radius 10, passing through the vertex of the converging flanks 4 and 6, includes with these flanks twoangles 'y and 8 which are the complements of angles a and B, respectively, and which are therefore also equal to each other.

As the groove 7 leaves the rib 3 just formed on the advancing rod, its forward flank 4 exerts a rearward thrust upon the rib so as to tilt it backwardly as illustrated in FIG. 4. A median line 11 of the rib, formerly coinciding with radius 10, is now rearwardly curved while the radius of curvature at the leading edge has increased and that at the trailing edge has decreased.

In the specific case of a rod with a diameter of 26 mm and an exit speed exceeding the entrance speed by 5.5 percent, the front radius R equaled l.4r while the rear radius R equaled 0.855; the corresponding root angles were 0.920: at the front and 1.083 at the rear. This represents, for an original root angle a fi= 60, a front angle of 55 and a rear angle of 65.

If the speed difierential increases to 7 percent, R grows to 1.5r whereas R, drops to 0.8r the leading and trailing root angles become 52 and 69, respectively, if the flank angle of the groove is 60.

FIGS. 5 and 6 illustrate the present improvement according to which, under otherwise unchanged conditions, the roller 1 (and, correspondingly, its companion roller 1') is modified so that radii of curvature r and r, are no longer identical. With a speed differential of 4 percent to 7 percent, as assumed above, r ranges between 0.75r, and 0.5r, in order to produce substantially identical radii R and R, in the finished rod. On the other hand, the root angles a, and )8, are now unequal, with a, ranging under the assumed conditions between 1.050: and 1.1504 and with B, ranging between 0.953 and 0.8513 where a and B are the desired, possibly identical, angles at the root of the completed rib 3.

Under these circumstances, the bisector 110 of the groove assumes a curved shape whereas the median line 1 1 1 of the rib is substantially perpendicular to its baseline as shown in FIG. 6.

The foregoing teachings are also applicable where the rounds at the root of the rib are to have different radii of curvature, with proportional changes in the reduced magnitude of the front radius and the increased magnitude of the rear radius of the roller grooves.

What is claimed is:

1. In a rolling mill for deforming cylindrical metal rods to provide them with generally transverse surface ribs, including a pair of counterrotating rollers with complementary peripheral channels of substantially semicircular cross-section having generally transverse grooves for shaping the ribs, the improvement wherein each groove is faired into the channel surface of its roller along a rounded leading edge and a rounded trailing edge as seen in the direction of rotation of the roller, the round of said leading edge having a substantially smaller radius of curvature than the round of said trailing edge.

2. The improvement defined in claim 1 wherein said radius of curvature at said leading edge ranges between substantially three-fourths to one-half of said radius of curvature at said trailing edge.

3. The improvement defined in claim 1 wherein each groove has a front flank and a rear flank extending substantially tangentially inwardly toward a vertex from said leading and trailing edges, respectively; said front flank including with the roller radius through said vertex, in a plane of symmetry of the roller transverse to its axis, an angle substantially smaller than the angle included in said plane between said roller radius and said rear flank.

4. A method of deforming a cylindrical metal rod to provide same with generally transverse surface ribs with predetermined radii of curvature at the roots of their flanks, comprising passing said rod between two counterrotating rollers with complementary peripheral channels of substantially semicircular cross-section having generally transverse grooves for shaping the ribs, each groove being faired into the channel surface of its roller along a rounded leading edge and a rounded trailing edge as seen in the direction of rotation of the roller, the round of said leading edge having a radius of curvature substantially smaller than the radius of curvature at the front root of said ribs, the round of said trailing edge having a radius of curvature substantially larger than the radius of curvature at the rear root of said ribs.

5. A method as defined in claim 4 wherein said rollers are so shaped and spaced with reference to said rod as to extrude the latter from the nip of said rollers at a velocity exceeding by 4 percent to 7 percent the speed of advance of the rod toward the rollers, the radius of curvature at said leading edge ranging between substantially three-fourths and one-half of said radius of curvature at said trailing edge.

6. A method as defined in claim 4, for imparting to each rib a symmetrical profile in an axial plane bisecting the rod, wherein each groove has a front flank and a rear flank extending substantially tangentially inwardly toward a vertex from said leading and trailing edges, respectively, said front flank including with the roller radius through said vertex in said axial plane a leading angle substantially smaller than the trailing angle included in said plane between said roller radius and said rear flank.

1i i i i t 

1. In a rolling mill for deforming cylindrical metal rods to provide them with generally transverse surface ribs, including a pair of counterrotating rollers with complementary peripheral channels of substantially semicircular cross-section having generally transverse grooves for shaping the ribs, the improvement wherein each groove is faired into the channel surface of its roller along a rounded leading edge and a rounded trailing edge as seen in the direction of rotation of the roller, the round of said leading edge having a substantially smaller radius of curvature than the round of said trailing edge.
 2. The improvement defined in claim 1 wherein said radius of curvature at said leading edge ranges between substantially three-fourths to one-half of saId radius of curvature at said trailing edge.
 3. The improvement defined in claim 1 wherein each groove has a front flank and a rear flank extending substantially tangentially inwardly toward a vertex from said leading and trailing edges, respectively; said front flank including with the roller radius through said vertex, in a plane of symmetry of the roller transverse to its axis, an angle substantially smaller than the angle included in said plane between said roller radius and said rear flank.
 4. A method of deforming a cylindrical metal rod to provide same with generally transverse surface ribs with predetermined radii of curvature at the roots of their flanks, comprising passing said rod between two counterrotating rollers with complementary peripheral channels of substantially semicircular cross-section having generally transverse grooves for shaping the ribs, each groove being faired into the channel surface of its roller along a rounded leading edge and a rounded trailing edge as seen in the direction of rotation of the roller, the round of said leading edge having a radius of curvature substantially smaller than the radius of curvature at the front root of said ribs, the round of said trailing edge having a radius of curvature substantially larger than the radius of curvature at the rear root of said ribs.
 5. A method as defined in claim 4 wherein said rollers are so shaped and spaced with reference to said rod as to extrude the latter from the nip of said rollers at a velocity exceeding by 4 percent to 7 percent the speed of advance of the rod toward the rollers, the radius of curvature at said leading edge ranging between substantially three-fourths and one-half of said radius of curvature at said trailing edge.
 6. A method as defined in claim 4, for imparting to each rib a symmetrical profile in an axial plane bisecting the rod, wherein each groove has a front flank and a rear flank extending substantially tangentially inwardly toward a vertex from said leading and trailing edges, respectively, said front flank including with the roller radius through said vertex in said axial plane a leading angle substantially smaller than the trailing angle included in said plane between said roller radius and said rear flank. 